Absorbent products, such as disposable diapers or incontinence inserts, generally have been manufactured by a process where discrete parts or components, such as absorbent materials, leg elastics, waist elastics, tapes, and other fasteners such as hook and loop materials or snaps, have been applied to a continuously moving web. Often, the speed at which the parts are fed into the process is not the same as the speed of the product web itself is traveling. Thus, the speed of the parts must be changed to match the speed of the product web to properly apply the parts without adversely affecting the process or the finished discrete parts.
A prior apparatus for applying discrete parts to a moving web is disclosed is in U.S. Pat. Nos. 5,716,478 and 5,759,340, both issued to Boothe et al. The apparatus includes a mechanism for severing a first substrate web traveling at a first speed into discrete parts and applying the discrete parts onto a second substrate web traveling at a second speed. The apparatus includes at least one transfer assembly which is configured to rotate about a first axis. The transfer assembly includes an outer surface which is configured to receive the discrete parts and apply the discrete parts to the second substrate web. The apparatus also includes a drive member which is configured to rotate about a second axis which is offset from the first axis of the transfer assembly. At least one coupler arm is pivotally connected to the drive member about a pivot point located radially outward from the second axis. The coupler arm includes a cam end which is configured to follow a predetermined curvilinear path and a crank end which is slidably connected to the transfer assembly. A drive mechanism is configured to rotate the drive member about the second axis. As the drive member is rotated, the cam end of the coupler arm is guided along the curvilinear path and the crank end of the coupler arm slidably engages the transfer assembly thereby pivoting the coupler arm about the pivot point to vary an effective drive radius of the transfer assembly and rotate the transfer assembly at a variable speed. In use, the transfer assembly is configured to maintain a substantially constant first surface speed as the discrete parts are received and a substantially constant second surface speed as the discrete parts are applied to the second substrate web.
Although the apparatus disclosed in the Boothe et al. patents has shown to be very effective in applying discrete parts to a moving web, one problem arises in transferring discrete parts having a varying thickness. When discrete parts having a varying thickness are used, the discrete part may only be placed in contact with the moving web at the thickness portion of the discrete part. This may lead to less than optimal performance in transferring and securing the discrete part to the moving web, and may result in decreased equipment reliability.
Accordingly, there remains a need in the art for an apparatus that can effectively transfer a discrete part having a varying thickness to a moving web.